MEMS device with improved via support planarization

Abstract

A microelectromechanical (MEMS) device has a movable member supported above a substrate on a via support. The member and via support are fabricated integrally from first and second member forming layers. A first member forming layer forms a lower part of the member and supporting structure for the via support. First and second fill layers are deposited and patterned to form a plug that fills an inner cavity opening in the via structure. The plug is planarized to a planar part of the first member forming layer, and a second member forming layer is deposited over the first member forming layer and the planarized plug to form an upper part of the member. The via support may have a cavity filled by BARC layers.

What is claimed is: 
     
       1. A method of making a MEMS device, comprising:
 forming a via opening within a sacrificial support layer formed over a substrate; 
 depositing a first member forming layer over the sacrificial support layer, including as a liner within and partially filling the via opening; 
 depositing a first fill layer over the first member forming layer, including over the first member forming layer within and further partially filling the via opening; 
 depositing a second fill layer over the first fill layer including within the via opening, the second fill layer filling the via opening to a level above a top surface of the first member forming layer; 
 depositing a masking material over the second fill layer, and patterning the masking material to form a mask covering the filled via opening and extending for a given lateral distance beyond a top of the via opening; 
 patterning the first and second fill layers using the mask to form a raised protrusion with a given step height and lateral width at the top of the via opening; 
 removing the mask following the patterning of the first and second fill layers; 
 depositing a third fill layer over the patterned first and second fill layers to fill an indentation in the raised protrusion; 
 removing the raised protrusion to planarize a top surface of the filled via opening with the top surface of the first member forming layer; and 
 depositing a second member forming layer over the first member forming layer and over the planarized top surface of the filled via opening. 
 
     
     
       2. The method of  claim 1 , further comprising, after depositing the second member forming layer, patterning the first and second member forming layers to form a member. 
     
     
       3. The method of  claim 2 , further comprising, after forming the member, removing the sacrificial support layer leaving the member supported above the substrate by the lined and filled via. 
     
     
       4. The method of  claim 3 , wherein the MEMS device comprises a micromirror device, and the member comprises a mirror. 
     
     
       5. The method of  claim 4 , wherein the first and second member forming layers comprise first and second metal layers. 
     
     
       6. The method of  claim 1 , further comprising curing the first and second fill layers prior to depositing the masking material over the second fill layer. 
     
     
       7. The method of  claim 6 , further comprising curing the first fill layer prior to depositing the second fill layer. 
     
     
       8. The method of  claim 7 , further comprising curing the first and second fill layers after planarizing the top surface of the raised protrusion. 
     
     
       9. The method of  claim 1 , wherein the first and second fill layers comprise layers of Bottom Anti-Reflective Coating (BARC) material. 
     
     
       10. The method of  claim 9 , wherein the third fill layer comprises a layer of BARC material. 
     
     
       11. The method of  claim 1 , wherein patterning the first and second fill layers patterns removes all of the second fill layer apart from the raised portion. 
     
     
       12. The method of  claim 11 , wherein patterning the first and second fill layers leaves a reduced thickness of the first fill layer over the first member forming layer apart from the raised portion. 
     
     
       13. The method of  claim 12 , wherein removing the raised protrusion includes removing the reduced thickness of the first fill layer. 
     
     
       14. A method of making a MEMS device, comprising:
 forming a via opening within a sacrificial support layer formed over a substrate; 
 depositing a first metal layer over the sacrificial support layer, including as a liner within and partially filling the via opening; 
 depositing a first Bottom Anti-Reflective Coating (BARC) layer over the first metal layer, including over the first metal layer within and further partially filling the via opening; 
 curing the first BARC layer; 
 depositing a second BARC layer over the first metal layer including within the via opening, the second BARC layer filling the via opening to a level above a top surface of the first metal layer; 
 curing the second BARC layer; 
 depositing a masking material over the second BARC layer, and patterning the masking material to form a mask covering the filled via opening and extending for a given lateral distance beyond a top of the via opening; 
 patterning the first and second BARC layers using the mask to form a raised protrusion with a given step height and lateral width at the top of the via opening; 
 removing the mask following the patterning of the first and second BARC layers; 
 depositing a sacrificial fill layer over the patterned first and second BARC layers to fill an indentation in the raised protrusion; 
 after planarizing the filled indentation with the top surface of the raised protrusion, removing the raised protrusion to planarize a top surface of the filled via opening with the top surface of the first metal layer; and 
 depositing a second metal layer over the first metal layer and over the planarized top surface of the filled via opening. 
 
     
     
       15. The method of  claim 14 , further comprising, after depositing the second metal layer, removing the sacrificial support layer. 
     
     
       16. The method of  claim 15 , wherein the MEMS device comprises a micromirror, and further comprising patterning the first and second metal layers to form a mirror. 
     
     
       17. The method of  claim 16 , wherein the first BARC layer is cured prior to depositing the second BARC layer. 
     
     
       18. The method of  claim 17 , wherein the second BARC layer is cured prior to depositing the masking material. 
     
     
       19. The method of  claim 18 , further comprising again curing the first and second BARC layers after planarizing the top surface of the raised protrusion. 
     
     
       20. A MEMS device comprising a micromirror, the micromirror including:
 a substrate; 
 a first metal layer; 
 a second metal layer; 
 a first Bottom Anti-Reflective Coating (BARC) layer; and 
 a second BARC layer; 
 the first metal layer, second metal layer, first BARC layer and second BARC layer defining a mirror supported in elevated position above the substrate by a via support; the first metal layer having a planar portion configuring a lower part of the mirror and also having a depending portion configuring supporting structure of the via support and having an opening; the first BARC layer being formed over the depending portion of the first metal layer and partially filling the opening; the second BARC layer being formed over the first BARC layer and filling a remainder of the opening; the first and second BARC layers being planarized at top surfaces with the first metal layer planar portion; and the second metal layer being formed over the planar part of the first metal layer and over the planarized top surfaces of the first and second BARC layers; the second metal layer configuring an upper part of the mirror.